Cell Biology and Bioenergetics Revision Worksheet

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Part 1: Cell Biology and Transport

Questions 1–20. Total: 60 marks. Answer all questions. Show your working for calculations.

1. (1 mark) Which structure is found in a bacterial cell?

A. Nucleus

B. Chloroplast

C. Plasmid

D. Mitochondrion

2. (1 mark) Which organelle is the site of aerobic respiration?

A. Ribosome

B. Mitochondrion

C. Vacuole

D. Cell wall

3. (2 marks) Name two structures present in plant cells but not animal cells.

4. (2 marks) Give one adaptation of a sperm cell and explain how it helps the cell carry out its function.

5. (1 mark) Which statement about stem cells is correct?

A. They can never divide.

B. They are always specialised.

C. They can differentiate into other cell types.

D. They are found only in plants.

6. (3 marks) A cell image is 36 mm wide. Its actual width is 0.12 mm. Calculate the magnification. Show your working.

7. (3 marks) Explain the difference between diffusion, osmosis and active transport.

8. (3 marks) A student places potato cylinders in different sucrose solutions. The percentage change in mass is recorded: 0.0 mol/dm³: +18%; 0.2 mol/dm³: +6%; 0.4 mol/dm³: −2%; 0.6 mol/dm³: −15%. Estimate the concentration at which there is no net movement of water. Explain your answer.

Part 2: Cell Division, Photosynthesis and Respiration

9. (2 marks) Put these stages of the cell cycle in the correct order: cell grows; DNA replicates; nucleus divides; cytoplasm and cell membrane divide.

10. (3 marks) Describe two uses or potential uses of stem cells. Include one possible risk of stem cell treatment.

11. (3 marks) Write the word equation for photosynthesis. State where in a plant cell it takes place.

12. (4 marks) A student investigates the effect of light intensity on photosynthesis using pondweed. The distance from the lamp is changed and the number of oxygen bubbles produced in one minute is counted. Identify the independent variable, dependent variable and two control variables. Give one improvement to the method.

13. (4 marks) Explain what is meant by a limiting factor in photosynthesis. Describe how light intensity affects the rate of photosynthesis when light is the limiting factor.

14. (3 marks) A plant is kept in darkness for 48 hours before a leaf is tested for starch. Explain why the plant is kept in darkness.

15. (4 marks) Compare aerobic respiration with anaerobic respiration in human muscle cells. Include the products and energy release.

16. (3 marks) During exercise, a person’s breathing rate and heart rate increase. Explain how these changes help the muscles.

17. (4 marks) Explain why oxygen debt occurs after vigorous exercise and how the body repays it.

18. (3 marks) Respiration provides energy for metabolism. Give three examples of metabolic reactions or processes in cells.

19. (4 marks) A student measures the rate of photosynthesis at different carbon dioxide concentrations. The rate rises from 2 to 5 units between 0.02% and 0.08% carbon dioxide, then remains at 5 units up to 0.20%. Explain the pattern in the results.

20. (4 marks) Explain how the structure of a leaf is adapted for efficient photosynthesis. Include gas exchange, light absorption and transport.

Answer Section: Mark-Scheme-Style Answers

1. C, plasmid.

2. B, mitochondrion.

3. Any two from cell wall, chloroplasts and permanent vacuole. (1 mark each)

4. Award up to 2 marks for a suitable adaptation and linked function, for example: tail/flagellum helps it swim towards the egg; many mitochondria provide energy for movement; acrosome contains enzymes to digest the egg cell membrane.

5. C, they can differentiate into other cell types.

6. Magnification = image size ÷ actual size. 36 ÷ 0.12 = ×300. (3 marks)

7. Diffusion is the net movement of particles from high to low concentration. Osmosis is the net movement of water through a partially permeable membrane from a dilute solution to a more concentrated solution. Active transport moves substances against the concentration gradient using energy from respiration. (1 mark each)

8. Approximately 0.35 mol/dm³. The percentage change is positive at 0.2 mol/dm³ and negative at 0.4 mol/dm³, so zero change lies between these values. (3 marks)

9. Cell grows → DNA replicates → nucleus divides → cytoplasm and cell membrane divide. (2 marks)

10. Uses include treating blood disorders, replacing damaged tissue or researching diseases and medicines. A risk is rejection, uncontrolled cell division or tumour formation. (1 mark for each valid use, 1 mark for a valid risk)

11. Carbon dioxide + water → glucose + oxygen. It takes place in the chloroplasts. (3 marks)

12. Independent variable: distance from lamp/light intensity. Dependent variable: oxygen bubbles per minute/rate of photosynthesis. Control variables may include pondweed species and length, carbon dioxide concentration, temperature or volume of water. Improvement: repeat and calculate a mean, count oxygen volume instead of bubbles, or allow the plant to acclimatise. (4 marks)

13. A limiting factor is a factor that, when in short supply, limits the rate of photosynthesis. Increasing light intensity increases the rate because more light energy is available. The rate eventually becomes constant when another factor, such as carbon dioxide concentration or temperature, becomes limiting. (4 marks)

14. To destarch the plant by using up stored starch in respiration. This ensures that any starch detected was produced during the investigation by photosynthesis. (3 marks)

15. Aerobic respiration uses glucose and oxygen and produces carbon dioxide and water. It releases more energy. Anaerobic respiration in muscles does not use oxygen, produces lactic acid and releases less energy. (4 marks)

16. Faster breathing increases oxygen intake and removes carbon dioxide. A faster heart rate increases blood flow to muscles, delivering more oxygen and glucose for aerobic respiration and removing waste products. (3 marks)

17. During vigorous exercise, the oxygen supply may be insufficient, so muscles respire anaerobically and lactic acid builds up. Oxygen debt is the extra oxygen needed after exercise to remove the lactic acid. Increased breathing and heart rate supply this oxygen; the liver converts lactic acid into carbon dioxide and water. (4 marks)

18. Any three from growth, active transport, movement, building larger molecules, cell division, temperature regulation or keeping organs functioning. (1 mark each)

19. Carbon dioxide is limiting between 0.02% and 0.08%, so increasing its concentration increases the rate. Above 0.08%, another factor becomes limiting, so the rate stays constant. (4 marks)

20. Large surface area provides more light and allows efficient gas exchange. Thin leaves give a short diffusion distance. Palisade cells contain many chloroplasts to absorb light. Stomata allow carbon dioxide in and oxygen out. Veins transport water in the xylem and sugars away in the phloem. (4 marks)